Certain clinical and morphologic cardiac observations are described in 18 necropsy patients aged 33 to 58 years (mean 45) (14 women) with chronic hypercalcemia (11.6 to 34.4 mg/dl (19.4) from 1 to 9 years (mean 5). Primary hyperparathyroidism was present in 9 patients and secondary hyperparathyroidism in the other 9 (of renal origin in 7). Cardiac valve anular and coronary arterial calcific deposits were present in 10 patients (group I) including 4 (mean age 51 years) with considerable narrowing of 2 or 3 of the 4 major epicardial coronary arteries. None of the other 8 patients (group II) had cardiac valve anular or cuspal calcific deposits and only 2 had coronary calcific deposits, small in each, and none had significant coronary luminal narrowing. Calcium was located in the media ("medial calcinosis"), with or without intimal deposition,of the coronary arteries in 5 patients. Comparision of the group I to the group II patients disclosed similar mean ages, durations of hypercalcemia and serum calcium levels, but significantly (p less than .05) higher mean total serum cholesterol levels (216-vs-163 mg/dl) and heart weights (426-vs-320 grams).